Firearms are usually aimed by a shooter using one eye to align the front and rear sights with a target. However, when aiming at fast moving targets such as flying game birds, the shooter may not have enough time to align front and rear sights. Consequently, some firearms, and more particularly shotguns, have only a front sighting bead on the muzzle end of the barrel allowing the shooter to aim the firearm by pointing the barrel, instead of aligning front and rear sights. Shooters must avoid two problems when aiming a firearm having only a front sighting bead. First, the shooter must not use his non-aiming eye to align the front sighting bead with the target. Second, because the firearm lacks a rear sight to align with the front sighting bead, the shooter's aiming eye must be aligned with the barrel to view the sighting bead in a path substantially parallel to the barrel.
Most people have one eye that is more dominant than the other. Right handed people normally have a dominant fight eye, and left handed people normally have a dominant left eye. Some shooters, however, must shoulder their firearm oppositely from their dominant eye, so they aim with their weaker eye. This usually occurs when left handed shooters use firearms intended for fight handed people or when fight handed shooters have a dominant left eye. Because most shooters prefer to keep their non-aiming eye open to view the target, these shooters usually have a tendency to use their dominant, non-aiming eye to align the sighting bead or the end of the barrel with the target. This problem is known as dominant eye crossover.
Improper shoulder placement of the firearm is also a common problem encountered by shooters aiming a firearm having only a from sighting bead. If the butt end of the firearm is improperly shouldered, the shooter's aiming eye will not be aligned with the barrel, and the alignment of the shooter's aiming eye and the front sighting bead will not correspond to the actual firing line of the firearm. Novice shooters and those shouldering their firearm oppositely from their dominant eye are likely to not even realize their mistake since the sighting bead remains visible even when the firearm is improperly shouldered.
Several prior art devices have attempted to overcome the problems associated with dominant eye crossover. For example, U.S. Pat. No. 3,974,586 to Kappner discloses a blinder, in the form of a thin strip, which extends rearwardly and to one side of the front sighting bead to block it from view of the non-sighting eye. The shooter's accuracy can still be reduced if his dominant eye is used to align the end of the barrel with the target. Moreover, the '586 device does not prevent improper shouldering of the firearm.
U.S. Pat. No. 5,056,909 to Brown et at. and U.S. Pat. No. 5,052,794 to Brown et at. disclose contact lenses having a central region to cover the pupil of the dominant eye to sufficiently blur the image normally seen by the dominant eye. Dominant eye crossover is eliminated, but the shooter's non-aiming eye cannot be used to view the target because his vision is blurred.
U.S. Pat. No. 4,761,196 to Brown et at. discloses a thin flexible disk that can be placed on the optical lenses of the shooter's glasses to partially block the view of the shooter's dominant eye. The view of the sighting bead is blocked, so dominant eye crossover is eliminated. However, the device obstructs the view of the shooter's non-aiming
U.S. Pat. No. 4,695,159 to Cannon discloses a sight for a firearm in which the shooter looks into the sight with his dominant eye while viewing the whole of the target area with the other eye. A light spot produced by the sighting device will appear to the observer to be superimposed on the target.